1. Field of the Invention
This invention relates generally to means for evacuating waste fluid from closed wounds or the like and more specifically to portable means for applying continuous suction to such a closed wound and to thereby draw waste fluid therefrom.
2. Description of the Prior Art
Various means have been developed for applying continuous suction to a closed wound to thereby draw waste fluid therefrom. Perhaps the most common method of applying continuous suction to a closed wound is by positioning one end of a hollow tube within the closed wound and attaching the other end of the hollow tube to an outlet of a central vacuum system as is typically provided on the walls of hospital rooms or to a portable electrical aspirator. This method is satisfactory where the patient is bedridden, but is not satisfactory where the patient is ambulatory. Portable evacuation devices have been developed for use where the patient is ambulatory. See, for example, McElvenny et al., U.S. Pat. Nos. 3,115,138; Mondiadis, 3,376,868; Lloyd et al., 3,572,340; and Treace, 3,871,377. The McElvenny et al patent discloses an evacuation device in which spring members are enclosed within an expandable chamber so that when the chamber is compressed and subsequently released, the spring members will cause it to expand and thereby create a vacuum within the interior of the chamber. The Mondiadis patent discloses an evacuation device in which the walls of an expandable chamber are resilient so that when the chamber is compressed and subsequently released, the walls of the chamber will cause it to expand and thereby create a vacuum within the interior of the chamber. The Lloyd and Treace patents disclose evacuation devices in which resilient foam material is enclosed within a collapsible container so that when the container is compressed and subsequently released, the resilient property of the foam material will cause the container to expand and thereby create a vacuum within the interior of the container. While these devices do provide portable evacuation of closed wounds on ambulatory patients, they do not perform entirely satisfactorily. One problem with such evacuation devices is the uneveness of the strength and duration of the suction applied to the closed wound. One reason for this is because these evacuation devices require the expansible means (i.e., the spring members, the walls of the expandable chamber, and the resilient foam material) to be manually compressed and the strength and duration of the vacuum created by the subsequent expansion of the expansible means is determined by how much it was compressed which is, in turn, largely determined by the strength of the person doing the compressing. Thus, with persons of varying strength compressing such a device, the strength and duration of the vacuum created thereby varies. Another problem with such devices occurs when it is desired to use the portable evacuation device in conjunction with a central vacuum unit when a patient is ambulatory only part of the time. Prior portable evacuation devices were adapted to be used in conjunction with a central vacuum unit or the like by allowing a tube to be selectively attached between the interior of the portable evacuation device and the central vacuum unit so that the central vacuum unit could draw waste fluid from the closed wound through the portable evacuation device (e.g., see lines 42-55 of col. 10 of the Lloyd et al patent). However, such a method is disadvantageous in that substantial amounts of the waste fluid is dissipated in the interior of the portable evacuation device as it is drawn therethrough.